The present invention relates to a transferring device for a semiconductor wafer, which device locates a semiconductor wafer in a predetermined position and then transfers it to the desired position. The transferring device can be used in the process of manufacturing or inspecting semiconductor wafers.
There is a need to transfer parts, such as semiconductor wafers, and stop them at a predetermined position, or alternatively, to change or correct the stop position and maintain the correct position.
Particularly, it is essential to stop a part or an object to be inspected or worked on at a predetermined position. And for determining the stop position, positioning stoppers have been used. In such conventional stoppers, it is usual that parts to be inspected hit against a stopper and are stopped there, and after the stopper is retracted from the parts path, the part is then allowed to move further. Usually the stopper retracts from the path of the parts while rubbing against the parts.
In most cases, manufacturing and inspection processes of semiconductor wafers are preformed in a clean room. Damages might be caused to the wafers. Not only this, there has been the problem of generation of dust by the rubbing between the semiconductor wafers and the conventional movable stopper.
There has been therefore a proposal for a stopper which does not rub the semiconductor wafers, or parts when retracting.
FIG. 1 is a schematic view for explaining such a conventional stop position determining device for parts, according to the above proposal.
In that device, a conveying belt 3 feeds parts 1 from left to right in the figure. In the case of the above mentioned conventional stopper which causes rubbing by the stopper, the stopper is allowed to move only in the Y direction shown in the figure. In this proposal (FIG. 1), a stopper 5 is driven to be able to move both in the X and Y directions by the respective X axis drive source 6 and Y axis driving source 8.
When the stopper 5 protrudes at the position shown in FIG. 1 and shown with slanting lines, the part 1 hits against the stopper 5 and is stopped by it. At the state when the belt 3 is stopped, the stopper 5 is moved to the right (in the figure) by the X-axis drive source 6, and then is lowered downwardly by the Y-axis drive source 8. Thus the stopper 5 moves away from the parts 1 to allow a further conveying thereof.
When the stopper 5 passes the position shown in FIG. 1 and is stopped there, it is possible to protrude the stopper 5 by the Y-axis drive source 8 at a further remote position, and then to bring it back to the left in the figure by the X-axis drive source 6 to stop it there.
The device of FIG. 1 can solve the problem of rubbing, if operated correctly, as explained. However, the above conventional device requires two drive sources 6 and 8 for the respective lateral (in the X direction) and vertical (in the Y direction) movements of the stopper 5.
Further, if the sequence of driving the sources 6 and 8 is not correctly performed, there might occur a problem of rubbing of parts at the time of vertical movement of the stopper 5 by the Y-axis drive source 8.
On the other hand, there is a need handle a part such as a semiconductor wafer whose angular position once trued up is desired to be rotated through example, for 180.degree. for the next working process. In such a positioning mechanism for transferring parts through 180 degrees by rotation, a pulse motor has been used. In a pulse motor, a high resolution drive can be carried out. The resolution may be improved by stepping down, and for further improving the resolution, it is possible to provide an encoder, so as to feed-back a signal.
With such a structure, a more precise transfer through 180 degrees may be possible, but the stucture of the system is complicated and expensive to manufacture.
An object of the present invention is, therefore, to provide a transferring device for a semiconductor wafer having a stop position determining device for parts such as semiconductor wafers, which can solve the above-mentioned problems with a rather simple structure.
Another object of the present invention is to provide a transferring device for a semiconductor wafer with a conveying arm having a position determining mechanism, which can rotate parts, precisely through a determined angle with a simple structure.